Sales of electronic equipment are influenced not only by its functions but also by its exterior designs, especially when such electronic equipment is a product for individual end users. For example, when the electronic equipment is an entertainment apparatus used for games, music reproduction, video reproduction or telecommunication, such electronic equipment is largely influenced by its external design in particular.
Therefore, external designs are carefully determined. Once the external design is determined and a product is released to the market, it is not desirable to change the external design because the design itself establishes an identity as a symbol of the entertainment apparatus. Moreover, even if the electronic equipment maintains the same external design, for example, changing its size without careful consideration may cause the equipment to lose compatibility with accessories such as external attachments. A casing embodying the external design must be therefore basically unchanged for a lifecycle of the entertainment apparatus.
However, speed of technological progress of the electronic equipment is very fast as compared with the lifecycle of the entertainment apparatus. An entertainment apparatus of this kind tends to be desired to show higher performance based on advanced technologies in reproducing beautiful animations with more reality and in executing technologically advanced games.
Therefore, design change is sometimes desired for applying parts with higher performance than those adopted at the time of its release. Moreover, as a style of usage of the entertainment apparatus has become diversified, some users demand mounting of an apparatus having a new function such as an external storage device, a communication apparatus and the like.